Hermetic optical fiber alignment assembly having integrated optical element

ABSTRACT

A hermetic optical fiber alignment assembly includes a ferrule portion having a plurality of grooves receiving the end sections of optical fibers, wherein the grooves define the location and orientation of the end sections with respect to the ferrule portion. The assembly includes an integrated optical element for coupling the input/output of an optical fiber to the opto-electronic devices in the opto-electronic module. The optical element can be in the form of a structured reflective surface. The end of the optical fiber is at a defined distance to and aligned with the structured reflective surface. The structured reflective surfaces and the fiber alignment grooves can be formed by stamping.

PRIORITY CLAIM

This application claims the priority of U.S. Provisional PatentApplication No. 61/623,027 filed on April 11, 2012, and U.S. ProvisionalPatent Application No. 61/699,125 filed on September 10, 2012. Further,this application claims the priority and is a continuation-in-part ofU.S. patent application Ser. No. 13/786,448 filed on Mar. 5, 2013, whichclaims the priority of U.S. Provisional Patent Application No.61/606,885 filed on Mar. 5, 2012. These applications are fullyincorporated by reference as if fully set forth herein. All publicationsnoted below are fully incorporated by reference as if fully set forthherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical fiber ferrule structures, inparticular a hermetic optical fiber alignment assembly including aferrule for aligning optical fibers.

2. Description of Related Art

Given the increasing bandwidth requirements for modern day datatransmission (e.g., for high definition video data), fiber optic signaltransmissions have become ubiquitous for communicating data. Opticalsignals are transmitted over optical fibers, through a network ofoptical fibers and associated connectors and switches. The opticalfibers demonstrate a significantly higher bandwidth data transmissioncapacity and lower signal losses compared to copper wires for a givenphysical size/space.

In fiber optic signal transmission, conversions between optical signalsand electrical signals take place beyond the terminating end of theoptical fiber. Specifically, at the output end of an optical fiber,light from the optical fiber is detected by a transducing receiver andconverted into an electrical signal for further data processingdownstream (i.e., optical-to-electrical conversion). At the input end ofthe optical fiber, electrical signals are converted into light to beinput into the optical fiber by a transducing transmitter (i.e.,electrical-to-optical conversion).

The opto-electronic devices (receiver and transmitter and associatedoptical elements and electronic hardware) are contained in anopto-electronic module or package. The optical fiber is introduced fromoutside the housing of the opto-electronic module, through an openingprovided in the housing wall. The end of the optical fiber is opticallycoupled to the opto-electronic devices held within the housing. Afeedthrough element supports the portion of the optical fiber throughthe wall opening. For a variety of applications, it is desirable tohermetically seal the opto-electronic devices within the housing of theopto-electronic module, to protect the components from corrosive media,moisture and the like. Since the package of the opto-electronic modulemust be hermetically sealed as whole, the feedthrough element must behermetically sealed, so that the electro-optic components within theopto-electronic module housing are reliably and continuously protectedfrom the environment.

Heretofore, hermetic feedthrough is in the form of a cylindrical sleevedefining a large clearance through which a section of the optical fiberpasses. The optical fiber extends beyond the sleeve into theopto-electronic module. The end of the optical fiber is terminated in aferrule (separate from the sleeve) that is aligned with theopto-electronic devices provided therein. A sealing material such asepoxy is applied to seal the clearance space between the optical fiberand inside wall of the sleeve. The sleeve is inserted into the openingin the opto-electronic module housing, and the opening is sealed,typically by soldering the exterior wall of the sleeve to the housing.The outside wall of the sleeve may be gold plated to facilitatesoldering and improve corrosion resistance.

Given the large clearance between the sleeve and the optical fiber andthe use of epoxy to seal such clearance (i.e., a layer of epoxy betweenthe external fiber wall and the inside wall of the sleeve), the sleevedoes not support the optical fiber with any positional alignment withrespect to the sleeve. Given the sealing material provides stress andstrain relief for the section of optical fiber held therein, the brittlefiber does not easily break during handling. The sleeve essentiallyfunctions as a grommet or conduit that is sealed to the opto-electronicmodule housing and that passes through the optical fiber in a hermeticseal within the sleeve. As noted below, the end of the optical fiberneeds to be aligned to the opto-electronic devices to within acceptabletolerances by means of a ferrule.

To optically couple the input/output of the optical fiber to theopto-electronic devices in the opto-electronic module, optical elementssuch as lenses and mirrors are required to collimate and/or focus lightfrom a light source (e.g., a laser) into the input end of the opticalfiber, and to collimate and/or focus light from the output end of theoptical fiber to the receiver. To achieve acceptable signal levels, theend of the optical fiber must be precisely aligned at high tolerance tothe transmitters and receivers, so the optical fiber are preciselyaligned to the optical elements supported with respect to thetransmitters and receivers. In the past, given the internal opticalelements and structures needed to achieve the required opticalalignments at acceptable tolerance, coupling structures including aconnection port is provided within the hermetically sealedopto-electronic module housing to which a ferrule terminating the end ofthe optical fiber is coupled. The transmitters and receivers andassociated optical elements and connection structures are thereforegenerally bulky, which take up significant space, thereby making themnot suitable for use in smaller electronic devices. Heretofore,opto-electronic modules containing transmitters and receivers aregenerally quite expensive and comparatively large in size for a givenport count. Given optical fibers are brittle, and must be handled withcare during and after physical connection to the coupling structurewithin the opto-electronic module and to avoid breakage at thefeedthrough sleeve. In the event of breakage of the optical fiber, ithas been the industry practice to replace the entire opto-electronicmodule to which the hermetic optical fiber feedthrough is soldered. Theconnection and optical alignment of the optical fibers with respect tothe transmitters and receivers must be assembled and the components mustbe fabricated with sub-micron precision, and should be able to beeconomical produced in a fully automated, high-speed process.

The above noted drawbacks of existing fiber optic data transmission areexacerbated in multi-channel fiber transmission.

OZ Optics Ltd produces multi-fiber hermetically sealable patchcord withglass solder having multiple optical fibers passing through a sleeve,with the optical fibers extending beyond the sleeve, with the ends ofthe optical fibers held in an alignment ferrule separate from thesleeve. OZ Optics Ltd further produces a multi-fiber hermeticallysealable patchcord with metal solder, in which the optical fibers arecoated with a metal (metalized fibers). The optical fibers areterminated with a silicon ferrule that is supported within a sleeve,which is a component separate from the ferrule. The outside wall of thesleeve is gold plated for sealing to an opto-electronic module housing.However, these multi-fiber hermetic feedthrough configurations do notappear to resolve the drawbacks of the prior art noted above, andintroduce additional complexity and cost at least from amanufacturability perspective.

What is needed is an improved hermetic optical fiber alignment assembly,which improves optical alignment, manufacturability, ease of use,functionality and reliability at reduced costs.

SUMMARY OF THE INVENTION

The present invention provides an improved hermetic optical fiberalignment assembly, which improves optical alignment, manufacturability,ease of use, functionality and reliability at reduced costs, therebyovercoming many of the drawbacks of the prior art structures.

In one aspect, the present invention provides a hermetic optical fiberalignment assembly, comprising: a first ferrule portion having a firstsurface provided with a plurality of grooves receiving at least the endsections of a plurality of optical fibers, wherein the grooves definethe location and orientation of the end sections with respect to thefirst ferrule portion; a second ferrule portion having a second surfacefacing the first surface of the first ferrule, wherein the first ferruleportion is attached to the second ferrule portion with the first surfaceagainst the second surface, wherein a cavity is defined between thefirst ferrule portion and the second ferrule portion, wherein the cavityis wider than the grooves, and wherein a suspended section of eachoptical fiber is suspended in the cavity, and wherein the cavity issealed with a sealant. The sealant extends around the suspended sectionsof the optical fibers within the cavity. At least one the first surfaceof the first ferrule portion is provided with a well defining a firstpocket in the first ferrule portion, wherein the first pocket and thesecond ferrule section together define the cavity. An aperture isprovided in at least one of the first ferrule portion and the secondferrule portion, exposing the cavity, wherein the sealant is feedthrough the aperture.

In another aspect of the present invention, the hermetic optical fiberalignment assembly provides optical alignment and a hermetic feedthroughfor an opto-electronic module. In a further aspect of the presentinvention, the hermetic optical fiber alignment assembly providesalignment and a terminal for access to an opto-electronic module.

In yet another aspect of the present invention, an improved hermeticoptical fiber alignment assembly includes an integrated optical elementfor coupling the input/output of an optical fiber to the opto-electronicdevices in the opto-electronic module. In one embodiment, the integratedoptical element comprises a reflective element that is stamped with thealignment groove for the optical fiber.

In one embodiment, the hermetic optical fiber alignment assembly,comprises a first ferrule portion defining an optical element and anoptical fiber retention structure (e.g., an alignment groove having anopen structure) such that an end face of the optical fiber is located ata predetermined distance from the optical element along the axis of theoptical fiber, wherein an end face of the optical fiber is located at apredetermined distance from the optical element along the axis of theoptical fiber, and wherein the optical fiber retention structureaccurately aligns the optical fiber with respect to the optical element,so that output light from the optical fiber can be directed by theoptical element to outside the first ferrule portion or input light fromoutside the first ferrule portion incident at the optical element can bereflected towards the optical fiber; and a second ferrule portionhermetically attached to the second ferrule portion, wherein the firstferrule includes an extended portion beyond an edge of the secondferrule portion, on which the optical element is located beyond the edgeof the second ferrule portion.

In another embodiment, the hermetic optical fiber alignment assemblycomprises a first ferrule portion having a first surface defining atleast a groove receiving at least an end section of an optical fiber,wherein groove defines the location and orientation of the end sectionwith respect to the first ferrule portion; a second ferrule portionhaving a second surface facing the first surface of the first ferrule,wherein the first ferrule portion is hermetically attached to the secondferrule portion with the first surface against the second surface,wherein the first ferrule includes an extended portion beyond an edge ofthe second ferrule portion, on which the groove extends and terminatesat an optical element located beyond the edge of the second ferruleportion, wherein an end face of the optical fiber is located at apredetermined distance from the optical element along the axis of theoptical fiber, and wherein the groove accurately aligns the opticalfiber with respect to the optical element, so that output light from theoptical fiber can be directed by the optical element to outside theferrule or input light from outside the ferrule incident at the opticalelement can be directed towards the optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of theinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings. In the following drawings, like referencenumerals designate like or similar parts throughout the drawings.

FIG. 1 is a schematic perspective view of an opto-electronic modulehousing, to which hermetic optical fiber assemblies are hermeticallysealed, in accordance with one embodiment of the present invention.

FIG. 2 is a schematic perspective view illustrating an optical jumperpatchcord having hermetic optical fiber assemblies, in accordance withone embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating the optical jumper patchcordin FIG. 2 with the hermetic optical fiber assembly hermetically sealedto an opto-electronic module housing, in accordance with one embodimentof the present invention.

FIGS. 4A to 4C are perspective views of the hermetic optical fiberassembly, in accordance with one embodiment of the present invention.

FIGS. 5A to 5C are plan views of the hermetic optical fiber assembly inFIG. 4; FIG. 5D illustrates an alternate embodiment.

FIG. 6 is an exploded perspective view of the hermetic optical fiberassembly in FIG. 4, in accordance with one embodiment of the presentinvention.

FIGS. 7A to 7E are plan views of the cover of the hermetic optical fiberassembly.

FIGS. 8A to 8E are plan views of the ferrule of the hermetic opticalfiber assembly.

FIGS. 9A to 9E are sectional views taken along lines 9A-9A to 9E-9E inFIG. 5A.

FIGS. 10A and 10B are perspective views of a light directing element atthe exit end of the optical fibers in the hermetic optical fiberassembly, in accordance with one embodiment of the present invention;FIG. 10C is a sectional view taken along line 10C-10C in FIG. 10B.

FIG. 11 is a schematic perspective view of an opto-electronic modulehousing, to which hermetic optical fiber assemblies are hermeticallysealed, in accordance with another embodiment of the present invention.

FIG. 12 is a photographic sectional view of a prototype of the hermeticoptical fiber assembly.

FIG. 13 is a sectional view showing addition detail of the mounting ofthe hermetic optical fiber assembly to the opto-electronic modulehousing, in accordance with another embodiment of the present invention.

FIG. 14 is a schematic perspective view of a hermetic optical fiberalignment assembly having an integral optical element, in accordancewith one embodiment of the present invention.

FIG. 15 is a schematic perspective view of the underside of the hermeticoptical fiber alignment assembly of FIG. 14.

FIG. 16 is an enlarged perspective view of the extended portion of theferrule, in accordance with one embodiment of the present invention.

FIG. 17A is a sectional view of the fiber alignment groove along alongitudinal axis of the optical fiber; FIG. 17B is a perspectivesectional view thereof.

FIG. 18 is a sectional view illustrating reflection of light betweenoptical fiber and an opto-electronic device, in accordance with oneembodiment of the present invention.

FIG. 19 is a sectional view illustrating reflection of light betweenoptical fiber and an opto-electronic device, in accordance with anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is described below in reference to various embodimentswith reference to the figures. While this invention is described interms of the best mode for achieving this invention's objectives, itwill be appreciated by those skilled in the art that variations may beaccomplished in view of these teachings without deviating from thespirit or scope of the invention.

The present invention provides an improved hermetic optical fiberassembly, which improves optical alignment, manufacturability, ease ofuse, functionality and reliability at reduced costs, thereby overcomingmany of the drawbacks of the prior art structures.

FIG. 1 is a schematic diagram of an opto-electronic module 12, to whichhermetic optical fiber assemblies 10 are hermetically sealed, inaccordance with one embodiment of the present invention. Theopto-electronic module 12 includes a housing 14, which includes a base16 and a cover hermetically sealed to the housing, protecting theinterior of the housing from the environment external of the housing.For simplicity, the cover of the opto-electronic module 12 is omitted inFIG. 1. Enclosed within chambers in the housing are opto-electronicdevices 17 and 18 (e.g., transmitter and receiver and associatedelectronics and/or optical elements (not specifically shown in FIG. 1,but schematically shown in FIG. 3). The electronics within theopto-electronic module 12 are electrically coupled to an externalcircuit board 20 via flexible electrical connection pins 19.

In the illustrated embodiment, the housing base 16 includes two openings21 and 22 through which the hermetic optical fiber assemblies 10 areinserted. In accordance with one aspect of the present invention, eachhermetic optical fiber assembly 10 serves as a hermetic feedthrough foroptical fibers 24 in a fiber ribbon 23. In the illustrated embodiment,there are four optical fibers 24 in the fiber ribbon 23. The hermeticoptical fiber assembly 10 also serves as a ferrule, which supports theends (i.e., a section or “end section”) of the optical fibers 24 in afixed position with respect to each other and with respect to theexternal surfaces of the hermetic optical fiber assembly 10. As will beelaborated further below, once the hermetic optical fiber assembly 10 isfixed attached to the housing 14 (e.g., by soldering at the opening (21,22) in base 16), the ends of the optical fibers 24 would be fixed inposition (i.e., precisely aligned) with respect to the opto-electronicdevices (17, 18) in the housing 14.

FIG. 2 is a schematic diagram illustrating an optical jumper patchcord30 having hermetic optical fiber assemblies 10, in accordance with oneembodiment of the present invention. FIG. 3 is a schematic diagramillustrating the optical jumper patchcord 30 with the hermetic opticalfiber assemblies 10 hermetically sealed to an opto-electronic modulehousing, in accordance with one embodiment of the present invention. Inthe illustrated embodiment, the optical jumper patchcord 30 includes twofiber ribbons 23, each terminating at one end with a hermetic fiberoptic assembly 10, and commonly terminating at another end with aconnector 25 for coupling to a fiber network. The connector 25 and theopto-electronic module 12 may be part of an opto-electronic peripheralboard, comprising a circuit board (not shown) that supports theopto-electronic module 12 and the connector 25 at an edge of the circuitboard. In which case, the optical jumper patchcord 30 serves as a shortoptical fiber connection from the opto-electronic module 12 to abuilt-in terminal (i.e., the connector 25) of the opto-electronicperipheral board for external connection to the fiber network orbackplane printed circuit board.

FIGS. 4 to 9 illustrate the detail structures of the hermetic opticalfiber assembly 10, in accordance with one embodiment of the presentinvention. The hermetic optical fiber assembly 10 is essentially aferrule assembly, having parallel open grooves provided therein foraligning the ends of the optical fibers 24.

FIGS. 4A to 4C are perspective views of the hermetic optical fiberassembly 10. FIGS. 5A to 5C are plan views of the hermetic optical fiberassembly 10. FIG. 6 is an exploded perspective view of the hermeticoptical fiber assembly 10. FIGS. 9A to 9E are sectional views takenalong lines 9A-9A to 9E-9E in FIG. 5A. In the illustrated embodiment,the ferrule assembly 10 comprises two ferrule portions, of which a firstferrule portion (hereinafter referred to as a ferrule 40) is providedwith optical fiber alignment grooves 34 and a second ferrule portion(hereinafter referred to as a cover 42) is not provided with anyalignment grooves. The ferrule portions each have a generally planarstructure (as compared to a tube or sleeve).

FIGS. 7A to 7E are plan views of the cover 42 of the hermetic opticalfiber assembly 10. Referring to FIG. 7A, the underside 38 of the cover42 (the side facing the ferrule 40) is provided with a shallow wellforming a pocket 44 near the center and a cutout 45 at one longitudinalend of the cover 42. Chamfers 46 are provided on the longitudinal edges.

FIGS. 8A to 8E are plan views of the ferrule 40 of the hermetic opticalfiber assembly 10. Referring to FIG. 8A, the underside 39 of the ferrule40 (the side facing the cover 42) is provided with a shallow wellforming a pocket 54 near the center and a cutout 55 at one longitudinalend of the ferrule 40, matching the pocket 44 and cutout 45. Parallellongitudinal grooves 34 in a horizontal plane parallel to the underside39 are provided between the end face 56 and the pocket 54. Additionalparallel longitudinal grooves 35 in a horizontal plane parallel to theunderside 39 are provided between the pocket 54 and cutout 55. Referringalso to FIG. 9E, the grooves 34 and 35 are sized to receive theterminating end sections of each optical fiber 24 (i.e., a short sectionof each optical fiber bear an end, in its bare state exposing thecladding layer, with protective buffer layer and jacket removed).Specifically, the grooves 34 are precisely sized to precisely positionthe ends of optical fibers 24 in relation to one another and theexternal surfaces of the ferrule 40. Upon attaching the hermetic opticalfiber assembly 10 to the housing 14 (e.g., by soldering at the opening(21, 22) in base 16), the ends of the optical fibers 24 would be fixedin position (i.e., precisely aligned) with respect to theopto-electronic devices (17, 18) in the housing 14.

As more clearly shown in FIG. 9E, when the cover 42 and the ferrule 40are mated together with the underside 38 of cover 42 and underside 39 offerrule 40 against each other, the pockets 44 and 45 together define acavity 48 through which a section of each optical fiber 24 is suspended(i.e., not touching the ferrule 40 and the cover 42. The ferrule 40 isprovided with an aperture 41, through which sealant can be feed into thecavity 48. Referring also to FIG. 9B, the width of the aperture 41 issubstantially wider than the diameter of an optical fiber 24, andextends across the ferrule to expose all the optical fibers 24 arrangedin parallel (see FIG. 4C; i.e., the width of the aperture 41 is widerthan all the grooves 34 combined in the plane of the ferrule 40).Further, the cutouts 45 and 55 together form a pocket 49 that receives astrain relief 43, which supports the fiber ribbon 24 (includingprotective layers over the bare optical fibers 24) at the other end ofthe assembly 10.

Referring to FIGS. 8D and 9A, the walls of the grooves 34 define agenerally U-shaped cross-section. The depth of each groove 34 is sizedto completely retain an optical fiber without protruding above thegroove 34, with the top of the optical fiber substantially in line withthe top of the groove (i.e., at substantially the same level as thesurface of the underside 39). When the cover 42 and the ferrule 40 aremated together with the underside 38 of cover 42 and underside 39 offerrule 40 against each other, the underside 48 of cover 42 just touchesthe top wall of the optical fibers as it covers over the grooves 34,thus retaining the optical fibers 24 in the grooves 34.

The grooves 34 are structured to securely retain the optical fibers 24(bare section with cladding exposed, without protective buffer andjacket layers) by clamping the optical fibers 24, e.g., by a mechanicalor interference fit (or press fit). For example, the width of thegrooves 34 may be sized slightly smaller than the diameter of theoptical fibers 24, so that the optical fibers 24 are snuggly held in thegrooves 34 by an interference fit. The interference fit assures that theoptical fibers 24 is clamped in place and consequently the position andorientation of the ends of the optical fibers 24 are set by the locationand longitudinal axis of the grooves 34. In the illustrated embodiment,the grooves 34 has a U-shaped cross-section that snuggly receive thebare optical fibers 24 (i.e., with the cladding exposed, without theprotective buffer and jacket layers). The sidewalls of the groove 34 aresubstantially parallel, wherein the opening of the grooves may beslightly narrower than the parallel spacing between the sidewalls (i.e.,with a slight C-shaped cross-section) to provide additional mechanicalor interference fit for the optical fibers 24. Further details of theopen groove structure can be found in copending U.S. patent applicationSer. No. 13/440,970 filed on Apr. 5, 2012, which is fully incorporatedby reference herein. The ferrule 40 having the grooves 34 is effectivelya one-piece open ferrule supporting the optical fibers 24 with theirends in precise location and alignment with respect to each other and tothe external geometry of the ferrule 40.

The grooves 34 may be provided with a rounded bottom in cross-section(see, FIG. 9A), which would conformally contact as much as half thecylindrical wall (i.e., semi-circular cylindrical wall) of the opticalfibers. In any event, the wall of the optical fibers 24 would come intocontact (e.g., compressive contact) with at least the side walls of thegrooves 34, with at least the lateral sides of the optical fibers intight contact (e.g., substantially tangential contact in cross-section)with the side walls of the grooves 34. Such lateral contact between theoptical fibers and adjacent sidewalls of the grooves 34 ensures ageometry that defines the necessary horizontal alignmentpositioning/spacing of the optical fibers 24 with respect to each otherand with respect to at least the lateral sides of the ferrule 40. Theprecise sizing of the depth of the grooves 34 in the ferrule 40 ensuresa geometry in reference to the cover 42 that defines the necessaryvertical alignment positioning of the optical fibers 24 with respect toat least the external surface (top surface opposite to the underside 39)of the ferrule 40.

Concerning the grooves 35 for retaining the section of the opticalfibers 24 further away from the ends of the optical fibers 24 on theother side of the cavity 48, they may have similar geometries and/ordesign considerations as the grooves 34. However, it is noted that forpurpose of optical alignment of the optical fibers, it is only necessaryto provide alignment grooves 34 having tight tolerance for supportingthe terminating end section of the optical fibers 24. The grooves 35provided nearer to the strain relief 43 need not have as strict atolerance compared to that of the grooves 34, as the tolerance of thegrooves would have no bearing on the optical alignment of the ends ofthe optical fiber 24 with respect to an external optical component.

The hermetic sealing of the assembly 10 can be implemented by thefollowing procedure, in accordance with one embodiment of the presentinvention. With the protective buffer and jacket layers removed at theend section, the optical fibers 24 is positioned into the grooves 34 and35 in the ferrule 40. The cover 42 is mated against the ferrule (e.g.,by an external clamping fixture) in the configuration illustratedgenerally by FIG. 9E. The cover 42 and ferrule 40 are soldered togetherusing gold-tin solder. The chamfer 46 provides some clearance to allowbleeding of excess solder. It is noted that the chamfer 46 is shown notto extend along the entire length of the cover 42, to reduce potentialclearance to facilitate soldering between the assembly 10 and the modulehousing 14.

Referring also to FIG. 13, a sealant 37 such as glass solder (or othersealant suitable for hermetic sealing) is feed through the aperture 41in the ferrule 40 as vacuum is applied to the pocket 49, thus drawingglass solder to fill the cavity 48 and available spaces/clearancebetween the optical fibers 23, the grooves 35 and the cover 42, giventhe grooves are generally U-shaped in cross-section. (See FIG. 13). Someof the glass solder also flows to fill available spaces between theoptical fibers, alignment grooves 34 and the cover 42. It is notnecessary to draw glass solder completely through the grooves 34 or 35,as long as there is sufficient sealant drawn to a sufficient distance toplug available spaces at least at a region near the entry from thecavity into the respective grooves. Given the pockets 44 and 54 havedepths deeper than the depths of the grooves 34 and 35, the sealantwraps around the sections of the optical fiber 24 suspended in thecavity 48. The sealant essentially forms a hermetic plug in the cavity48, restricting leakage through the assembly 10. The structure of theassembly 10 can be hermetically sealed without requiring any externalsleeve, beyond the two ferrule portions (ferrule 40 and cover 42 in theabove described embodiment). The structure of the hermetic assembly isthus very simple, which provides an effective hermetic seal.

It is noted that given the tight contact between the wall of the opticalfibers and the walls of at least the grooves 34, the sealant does notcome between the contact surfaces between the optical fibers 24, thecover 42 and the walls of groove 34 which were present prior to applyingthe sealant. It is intended that the sealant plugs available spacesand/or clearance between the optical fibers 24, grooves 34 and cover 42,but do not form an intermediate layer between the optical fibers and thegroove walls at the contact points prior to applying the sealant, whichcould otherwise affect the alignment of the optical fibers by thegrooves 34.

After sealing with the glass solder, an epoxy material is applied intothe pocket 49 to form the strain relief 43. The exposed ends of theoptical fiber 24 may be polished to be substantially coplanar with theend face 56 of the ferrule 40 to finish the hermetic assembly 10. Theends of the fibers 24 may protrude slightly (by at most a few microns)beyond the end face 56 of the ferrule 40 but do not extend appreciablybeyond the end face 56 because there is no protective buffer and jacketlayers at the respective ends of the optical fibers 24. To facilitatesoldering of the assembly to the module housing 14 and to improvecorrosion resistance, the surfaces of the cover 42 and/or the ferrule 40may be gold plated.

According to one aspect of the present invention, the ferrule 40 and/orthe cover 42 may be formed by precision stamping a metal material. Inone embodiment, the metal material may be chosen to have high stiffness(e.g., stainless steel), chemical inertness (e.g., titanium), hightemperature stability (nickel alloy), low thermal expansion (e.g.,Invar), or to match thermal expansion to other materials (e.g., Kovarfor matching glass). Alternatively, the material may be silicon, a hardplastic or other hard polymeric material.

The above disclosed open structure of the ferrule 40 and cover 42 lendsthemself to mass production processes such as stamping, which are lowcost, high throughput processes. A precision stamping process andapparatus has been disclosed in U.S. Pat. No. 7,343,770, which wascommonly assigned to the assignee of the present invention. This patentis fully incorporated by reference as if fully set forth herein. Theprocess and stamping apparatus disclosed therein may be adapted toprecision stamping the features of the ferrule 40 and cover 42 of thepresent invention. The stamping process and system can produce partswith a tolerance of at least 1000 nm.

FIG. 5D illustrates an alternate embodiment, in which complementaryalignment grooves 34′ and 34″ (e.g., grooves having C-shaped orsemi-circular cross-section) are provided on the ferrule portions 40′and 42′, respectively. The grooves 34′ and 34″ may be symmetrical orasymmetrical with respect to the contact interface between the ferruleportions 40′ and 42″ in the end view of FIG. 5D (or sectional vieworthogonal to the longitudinal axis of the grooves). The ferruleportions 40′ and 42″ may be identical in an alternate embodiment.Alternatively, grooves having V-shaped cross-section could be usedinstead of U-shaped or C-shaped grooves in the ferrule 40, cover 42,and/or ferrule portions 40′ and 42′.

Instead of providing an aperture in the ferrule 40 for feeding glasssolder, such aperture may be provided in the cover 42 instead, or inaddition. Further, the cavity 48 may be defined by a pocket provided inonly one of the ferrule 40 and the cover 42. Alternatively, instead ofwells defining the pockets 44 and 54, grooves of significant larger sizemay be provided in the cover 42 and/or ferrule 40 bridging the grooves34 and 35 (i.e., large clearances between optical fibers 24 and thelarger grooves to facilitate flow of sealant to hermetically, internallyplug the assembly).

While the above embodiments are directed to a hermetic multi-fiberferrule assembly, the present inventive concept is equally applicable toa hermetic single-fiber ferrule assembly.

FIGS. 10A and 10B are perspective views of a light directing element atthe end of the optical fibers 24 in the hermetic optical fiber assembly10 discussed above; FIG. 10C is a sectional view taken along line10C-10C in FIG. 10B. A separate mirror assembly 57 (schematically shown)is positioned and aligned with the ends of the optical fibers 24, todirect light input/output between the fiber ends and an opto-electronicdevice 58 (schematically shown), such as a transmitter (e.g., a lasersuch as a VCSEL—Vertical Cavity Surface-Emitting Laser) or a receiver(e.g., photodetector). These opto-electronic devices convert betweenelectrical signals and optical signals, and are contained in theopto-electronic module 12. FIG. 13 is a sectional view showingadditional detail of the mounting of the hermetic optical fiber assembly10 through the openings (21, 22) in the base 16 of opto-electronicmodule housing 14, in accordance with another embodiment of the presentinvention.

The mirror assembly 57 may be attached to the assembly 10, and theinput/output of the mirror assembly 57 is positioned and aligned withrespect to the opto-electronic device 58. Alternatively, the mirrorassembly 57 is supported within the module 12 and aligned with respectto the opto-electronic device 58, with the hermetic assembly 10 alignedto the mirror assembly 57. Reference also to FIG. 3, the hermeticassembly 10 is hermetically sealed to the module housing base 16. Thehermetic assembly 10 may be deemed to function both as a feedthrough andas an alignment ferrule for the optic fiber ribbon 23.

While the above described embodiments are described in reference to ahermetic ferrule assembly that has a generally rectangularcross-section, other cross-sectional geometry may be implemented withoutdeparting from the scope and spirit of the present invention.

Referring to embodiment illustrated in FIG. 11, the hermetic ferruleassembly may have a generally oval cross-section. The structure of thehermetic assembly 60 may be similar to the hermetic assembly 10 in theearlier embodiments, except that the external cross-sectional profile isgenerally oval. The hermetic assembly 60 includes two ferrule portionswhich together make up the hermetic assembly having the ovalcross-section. One of the ferrule portions may correspond to the cover42 in the prior embodiment (having similar surface features as theunderside 38) and the other one of the ferrule portions may correspondthe ferrule 40 in the prior embodiment (having similar surface featuresas the underside 39). In this embodiment, instead of providing thehermetic ferrule assembly connected to a optic fiber ribbon 23 as in theprior embodiments, the hermetic ferrule assembly 60 is hermeticallyattached to the housing 14 of the opto-electronic module 12, having onlybare optical fibers 24 (i.e., without buffer and protection layers) heldwithin the assembly 60 without extending at both ends appreciably beyondthe assembly 60 (i.e., the optical fibers held in the assembly 60terminates substantially coplanar with both end faces of the assembly60; one of the end faces of the assembly 60 being inside the modulehousing 14). In this embodiment, the fiber alignment grooves would beprecisely formed (e.g., by stamping) at high tolerance for both ends ofthe optical fibers. Alternatively, the oval hermetic assembly in FIG. 11may be replaced with the hermetic assembly 10 in the prior embodiment,in which case an alignment sleeve having a generally rectangularcross-section would be required.

Accordingly, in this embodiment, the hermetic ferrule assembly 60provides a demountable terminal for the module 12, for coupling toanother optical device, such as an optical fiber ribbon (e.g., a patchcord 63 having similarly shaped ferrules having oval cross-section), byusing an alignment sleeve 62 (e.g., a split sleeve having complementaryshape sized to receive the ferrule assembly 60 and the ferrule on thepatch cord 63). In this embodiment, the hermetic assembly 60 may bedeemed to be a hermetic terminal of the module 12 having an alignmentferrule for optical alignment to external devices. With this embodiment,a defective external optical fiber ribbon may be replaced by plugging areplacement fiber ribbon onto the hermetical ferrule terminal.

In yet another aspect of the present invention, an improved hermeticoptical fiber alignment assembly includes an integrated optical elementfor coupling the input/output of an optical fiber to the opto-electronicdevices in the opto-electronic module. Instead of a separate, externaloptical module (e.g., mirror module 57) in the embodiments of FIGS. 10and 13, the improved hermetic optical fiber alignment assembly includesan integrated optical element (e.g., the optical element and the ferruleportion are part of the same monolithic structure). In one embodiment,the integrated optical element comprises a reflective element that isstamped with the alignment groove for the optical fiber in the ferruleportion of the hermetic optical fiber alignment assembly. In theembodiments discussed below, the optical element is a structuredreflective surface that is an integral extension from the alignmentgroove in the ferrule in the above discussed embodiments of the hermeticoptical fiber alignment assemblies. The end of the optical fiber is at adefined distance to and aligned with the structured reflective surface.The reflective surface directs light to/from the input/output ends ofthe optical fiber by reflection. The open structure open structure ofthe structured reflective surface and fiber alignment groove lendsitself to mass production processes such as precision stamping.

The present invention adopts the concept of stamping optical elementsdisclosed in the earlier filed copending U.S. patent application Ser.No. 13/786,448 (to which priority has been claimed), which had beenfully incorporated by reference herein.

In the embodiment illustrated in FIGS. 14 and 15, the hermetic opticalfiber alignment assembly 110 has similar structure as the hermeticassembly 10 disclosed above, with the exception that instead ofterminating the optical fibers 24 at an end face of the assembly, theferrule is extended such that the alignment grooves extends tostructured reflective surfaces and the ends of the optical fibers 24 arepositioned in relation to the structured reflective surfaces. Thehermetic optical fiber alignment assembly 110 includes a ferrule 140 anda cover 142, which are essentially similar in structure to the ferrule40 and cover 142 in the prior embodiments, with the exception of theextended structure of the ferrule 140. The end of the ferrule 140 nearthe terminating ends of the optical fibers 24 is not coplanar with theend of the cover 142. The ferrule 142 has a portion 70 that extendsbeyond the adjacent end of the cover 142. Referring to FIG. 15, theferrule 142 is provided with fiber alignment grooves 134 that extendbeyond the edge of the cover to the extended portion 70. Each groove 134terminates in a structured reflective surface 113 located beyond theadjacent edge of the cover 142. Each optical fiber 124 extends in thegroove 134 to beyond the edge of the cover 142, to closer to thestructured reflective surface 113. FIG. 6 illustrates an enlarged viewof the extended portion 70.

FIG. 17A is a sectional view taken along the longitudinal axis of theoptical fiber 10. FIG. 17B is a perspective section view taken along thelongitudinal axis of the optical fiber 10. In the illustratedembodiment, the fiber alignment groove 134 positively receives theoptical fiber 24 in a manner with the end of the optical fiber 24 at adefined distance to and aligned with the structured reflective surface113. The location and orientation of the structured reflective surface113 is fixed in relation to the fiber alignment groove 134. In theillustrated embodiment, the groove 134 and the structured reflectivesurface 113 are defined on the same (e.g., monolithic) ferrule 140. Thegroove 134 has a section 124 defining a space between the end face 15 ofthe optical fiber 24. In the illustrated embodiment, this section 124has a similar width but a shallower bottom as the remaining sections ofthe groove 134. The section 124 defines a shoulder 127 that provides astop against which a portion (end) of the end face 113 of the opticalfiber 24 is butted. Accordingly, a distance (e.g., 245 μm) along theoptical axis is defined between the end face 115 and the structuredreflective surface 113. In the illustrated embodiment, the optical fiberis completely received in the groove 134, with the exterior surface ofthe optical fiber 24 flush with the top surface 139 of the ferrule 140.Given an optical fiber having a diameter of 125 μm, and a VCSEL lightsource 158 at an effective distance (e.g., from the flat surface of theVCSEL 158 along the optical axis) of 100 μm from the structuredreflective surface 113, the distance of the flat surface of the VCSEL158 from the top surface 139 of the ferrule would be about 37.5 μm.

The design considerations of the open groove 134 are similar to thegrooves 34 in the earlier embodiments (e.g., a generally U-shapedcross-section that snuggly receive the bare optical fiber 24, etc. Thedesign considerations for the structured reflective surface are similarto those disclosed in copending U.S. patent application Ser. No.13/786,448.

The hermetic assembly 110 is attached to the opening (21, 22) in thebase 16 of the housing 14 of the opto-electronic module 12, with theextended portion 70 within the module housing 14. The reflective surface113 is in optical alignment with the opto-electronic device 58. FIG. 18illustrates a close up sectional view of the structured reflectivesurface region. In this embodiment, the structured reflective surface isa flat mirror surface, which reflects light 159 to/from the opticalfiber 24 from/to the opto-electronic device 58. FIG. 19 is a sectionalview illustrating the reflection of light between optical fiber 24 andthe opto-electronic device 58 via structured reflective surface 113 atthe extended portion 70, which is a concave reflective surface thatreflect incident light in a converging manner.

The hermetic assembly 110 may be deemed to function as a feedthroughwith built-in optics and an alignment ferrule for the optic fiber ribbon23, eliminating the need for separate optical elements for opticalcoupling with the opto-electronic devices (e.g., transmitter andreceiver) in the opto-electronic module 12.

The structured reflective surface 113 and the alignment grooves 134 maybe formed integrally by precision stamping a ferrule out of a metalmaterial. A precision stamping process and apparatus has been disclosedin U.S. Pat. No. 7,343,770, which was commonly assigned to the assigneeof the present invention. This patent is fully incorporated by referenceas if fully set forth herein. The process and stamping apparatusdisclosed therein may be adapted to precision stamping the features ofthe ferrule 140 and/or cover 142 of the present invention (including thestructured reflective surfaces and optical fiber alignment grooves). Thestamping process and system can produce parts with a tolerance of atleast 1000 nm.

For the hermetic assemblies described above that are configured foroptical alignment/coupling to optical fibers in another fiber ribbon,the external surfaces of the hermetic assemblies should be maintained athigh tolerance as well for alignment using an alignment sleeve. In theembodiments described above, no alignment pin is required for alignmentof the ferrules. Accordingly, for stamping of the ferrule portions(ferrules and covers), that would include stamping the entire body ofthe ferrule portions, including forming the grooves, mating surfaces ofthe ferrule portions, and external surfaces that come into contact withsleeves. The sleeves may be precision formed by stamping as well. Thismaintains the required dimensional relationship between the grooves andexternal alignment surfaces of the hermetic assemblies, to facilitatealignment using alignment sleeves only without relying on alignmentpins.

In all the above described embodiments, the structured reflectivesurface 113 may be configured to be flat, concave or convex, or acombination of such to structure a compound reflective surface. In oneembodiment, the structured reflective surface has a smooth (polishedfinish) mirror surface. It may instead be a textured surface that isreflective. The structured reflective surface may have a uniform surfacecharacteristic, or varying surface characteristics, such as varyingdegree of smoothness and/or textures across the surface, or acombination of various regions of smooth and textured surfaces making upthe structured reflective surface. The structured reflective surface mayhave a surface profile and/or optical characteristic corresponding to atleast one of the following equivalent optical element: mirror, focusinglens, diverging lens, diffraction grating, or a combination of theforegoing. The structure reflective surface may have a compound profiledefining more than one region corresponding to a different equivalentoptical element (e.g., a central region that is focusing surrounded byan annular region that is diverging). In one embodiment, the structuredreflective surface is defined on an opaque material that does nottransmit light through the surface.

The hermetic assemblies described in earlier embodiments may be furtherprovided with an integral optical element in similar fashion. Forexample the hermetic assembly 60 in FIG. 11 may adopt an integraloptical element (e.g., a stamped structured reflective surface) similarto the assembly 110.

The hermetic optical fiber alignment assembly in accordance with thepresent invention overcomes many of the deficiencies of the prior art,which provides precision alignment, high reliability againstenvironmental conditions, and which can be fabricated at low cost. Theinventive hermetic assembly may be configured to support a single ormultiple fibers, for optical alignment and/or hermetic feedthrough thatmay include integral optical elements.

While the invention has been particularly shown and described withreference to the preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madewithout departing from the spirit, scope, and teaching of the invention.Accordingly, the disclosed invention is to be considered merely asillustrative and limited in scope only as specified in the appendedclaims.

We claim:
 1. A hermetic optical fiber alignment assembly, comprising: afirst ferrule portion having a first surface defining at least a groovereceiving at least an end section of an optical fiber, wherein groovedefines the location and orientation of the end section with respect tothe first ferrule portion; a second ferrule portion having a secondsurface facing the first surface of the first ferrule, wherein the firstferrule portion is hermetically attached to the second ferrule portionwith the first surface against the second surface, wherein the firstferrule includes an extended portion beyond an edge of the secondferrule portion, on which the groove extends and terminates at anoptical element located beyond the edge of the second ferrule portion,wherein an end face of the optical fiber is located at a predetermineddistance from the optical element along the axis of the optical fiber,and wherein the groove accurately aligns the optical fiber with respectto the optical element, so that output light from the optical fiber canbe directed by the optical element to outside the ferrule or input lightfrom outside the ferrule incident at the optical element can be directedtowards the optical fiber.
 2. The hermetic optical fiber alignmentassembly as in claim 1, wherein the optical element is integral to theferrule.
 3. The hermetic optical fiber alignment assembly as in claim 2,wherein the optical element and the ferrule are part of a samemonolithic structure.
 4. The hermetic optical fiber alignment assemblyas in claim 2, wherein the optical element comprises a structuredreflective surface, where the groove extends and terminates at thestructured reflective surface, wherein output light from the opticalfiber can be reflected by the structured reflective surface to outsidethe ferrule or input light from outside the ferrule incident at thestructured reflective surface can be reflected towards the opticalfiber.
 5. The coupling device as in claim 4, wherein the groove isaligned with respect to the structured reflective surface.
 6. Thecoupling device as in claim 5, wherein the groove includes a shoulderthat defines a stop to which a portion of the end face of the opticalfiber can butt against to define the predetermined distance between theend face of the optical fiber and the structured reflective surface. 7.The coupling device as in claim 6, wherein the groove is precisionformed to align the optical fiber with respect to the structuredreflective surface.
 8. The coupling device as in claim 7, wherein thegroove is an open groove on the first ferrule portion.
 9. The couplingdevice as in claim 8, wherein the structured reflective surface and theopen groove are formed by stamping a malleable material.
 10. Thecoupling device as in claim 9, wherein the malleable material is metal.11. The coupling device as in claim 1, wherein the structured reflectivesurface is concave.
 12. An opto-electronic module, comprising: ahousing; and a hermetic optical fiber alignment assembly as in claim 1,hermetically sealed to the housing.
 13. An opto-electronic module,comprising: a housing; and a hermetic optical fiber alignment assemblyas in claim 1, hermetically sealed to the house, forming a terminal forexternal connection by an alignment sleeve.
 14. The hermetic opticalfiber alignment assembly as in claim 1, wherein there are a plurality ofoptical fibers and a plurality of grooves each receiving at least theend section of one of the optical fibers, and each groove terminates ata structured reflective surface.
 15. A process of making the hermeticoptical fiber alignment assembly of claim 1, comprising: stamping aferrule to form a structured reflective surface and at least an opticalfiber alignment groove, wherein the groove is aligned with respect tothe structured reflective surface.
 16. A hermetic optical fiberalignment assembly, comprising: a first ferrule portion defining anoptical element and an optical fiber retention structure such that anend face of the optical fiber is located at a predetermined distancefrom the optical element along the axis of the optical fiber, wherein anend face of the optical fiber is located at a predetermined distancefrom the optical element along the axis of the optical fiber, andwherein the optical fiber retention structure accurately aligns theoptical fiber with respect to the optical element, so that output lightfrom the optical fiber can be directed by the optical element to outsidethe first ferrule portion or input light from outside the first ferruleportion incident at the optical element can be reflected towards theoptical fiber; and a second ferrule portion hermetically attached to thesecond ferrule portion, wherein the first ferrule includes an extendedportion beyond an edge of the second ferrule portion, on which theoptical element is located beyond the edge of the second ferruleportion.
 17. A hermetic optical fiber alignment assembly as in claim 16,wherein the optical fiber retention structure comprises an alignmentgroove sized to receive at least an end section of the optical fiber.